1. Field of the Invention
The present invention relates to a data transmission/reception method and apparatus thereof that is MPEG-2 based, transmitting and receiving input data, including at least video and audio data dependent upon the MPEG-2 standard. Wherein, the input data may also include xe2x80x9cuser dataxe2x80x9d containing xe2x80x9csystem dataxe2x80x9d, an xe2x80x9cerror correction codexe2x80x9d, an xe2x80x9cerror detection codexe2x80x9d, and other related connections. The audio data is not limited to xe2x80x9cuncompressed audio dataxe2x80x9d, extending to xe2x80x9caudio data, not dependent upon the MPEG-2 standardxe2x80x9d.
Note that the MPEG-2 stands for xe2x80x9cMoving Picture Experts Group 2xe2x80x9d, and is a world-wide standard, in terms of image compression.
2. Description of the Related Art
The conventional MPEG-2 based transmission/reception of MPEG-2 based video data(hereafter, referred to as merely xe2x80x9cvideo dataxe2x80x9d), uncompressed audio data, and user data are constructed in the following fashion: First, a transport stream is directly fabricated from a PES stream of the video data; another transport stream is then fabricated from a PES private stream of the uncompressed audio data; and yet another transport stream is fabricated from a PES private stream of the user data. Secondly, the fabricated transport streams are multiplexed sent and received.
xe2x80x9cPESxe2x80x9d stands for xe2x80x9cPacketized Elementary Streamxe2x80x9d, denoting a data stream such as packetized video/audio data, the format of which is defined in the MPEG-2 standard. The xe2x80x9cPES streamxe2x80x9d denotes a PES data stream, the format of which is defined in the MPEG-2 standard. The xe2x80x9ctransport streamxe2x80x9d denotes a stream mainly used in a transmission system, the format of which is also defined in the MPEG-2 standard. The xe2x80x9cPES private streamxe2x80x9d denotes a user-usable data stream, defined in the MPEG-2 standard.
In addition, an error correction code and an error detection code, unique to a recording apparatus, may be attached as user data to video data. In this case, since the combination of the video data, the error correction code, and the error detection code is against the MPEG-2 standard, they are conventionally transmitted and received by being put into a PES private stream, and a transport stream is then fabricated with the PES private stream.
Furthermore, in a data transmission/reception apparatus handling both the 525/59.94 component signal and the 625/50 component signal, different transport streams are fabricated with respective PES private streams for the component signals. Wherein, the xe2x80x9c525/59.94 component signalxe2x80x9d denotes a component video signal dependent upon the NTSC(National Television System Committee) color system, with 525 lines and a field frequency of 59.94 Hz. More specifically, it includes three primary-color signals of R(Red), G(Green), and B(Blue). Alternatively, it includes a luminance signal(Y) and color difference signals(Cb and Cr). Note that hereafter the xe2x80x9c525/59.94 component signal may be referred to as merely a xe2x80x9c525 signalxe2x80x9d. The xe2x80x9c625/50 component signalxe2x80x9d denotes a component video signal dependent upon the NTSC color system, with 625 lines and a field frequency of 50 Hz. Like the 525/59.94 component signal, the 625/50 component signal includes three primary-color signals of R(Red), G(Green), and B(Blue). Alternatively, it includes a luminance signal(Y) and color differential signals(Cb and Cr). Note that hereafter the xe2x80x9c625/50 component signal may be referred to as simply a xe2x80x9c625 signalxe2x80x9d,
In the conventional technologies, the ratios of video data, uncompressed audio data, and user data to a frame of video data are not fixed. Moreover, their locations to the frame are also not fixed. In addition, detection of a transport header is made, however it is not protected.
Many earlier technologies relevant to the present invention are disclosed. For example, Laid-open Hei-7-30854 (hereafter, referred to as reference 1) describes an xe2x80x9cimage signal encoding apparatusxe2x80x9d minimizing possible degradation of an encoded image quality, with a superior error-proof characteristic. Reference 1 describes: an image preprocessing unit that converts an image signal into an image signal with the format suitable for a low bit rate coding method; and an image coding unit that MPEG-based-encodes the converted image into the resulting encoded image data. A time-series data conversion unit then changes the time-series order of the encoded data into another, leading to decrease a possible encoding-error propagating area. Subsequently, a channel encoding unit attaches an error correction code, transmitting and recording the resultant data onto a transmission/recording medium. In regards to the conventional approaches, the possible encoding-error propagating area will be drastically reduced. This enables for successful fabrication of an image coding apparatus with a low bit rate coding and a high error-proof characteristic.
Laid-open Hei-5-119788 (hereafter, referred to as reference 2) discloses a xe2x80x9ctransmission/reception apparatusxe2x80x9d exactly reproducing audio data and image data, which has external noise-proof and robust against a low transmission cable quality. According to the reference 2, a RF modulation circuit of a transmission unit 2PSK-modulates reproduced and EFM-encoded sound data, image data, and time data, digitally transmitting them to a reception unit, via a transmission line. A RF demodulation circuit of the reception unit 2PSK-demodulates the transmitted sound data. An EFM decoder then RFM-demodulates the resulting demodulated sound data, correcting for error and de-interleaving it. Since transmitted data is digital data, it can be safely transmitted even though the quality of the transmission line is low. In addition, even though an external noise may have negative influence on the data, it will be exactly reproduced by EFM-demodulating, correcting for error, and de-interleaving the influenced data by the aforementioned EFM-decoder.
Laid-open Hei-4-79588 (hereafter, referred to as reference 3) discloses a xe2x80x9cdigital transmitted data signal processing apparatus and recording/reproduction apparatusxe2x80x9d, which can record an image and sound signals with a single format for both a high-speed recording and a normal-speed recording, on a magnetic tape by the following manner: First, the image and sound signals are compressed in their time axes. It is then compressed in terms of their bit length. Thirdly, a parity signal is attached to them. Lastly, they are subjected to modulation-processing, and then transmitted. According to the reference 3, the output signal of a compression circuit is received by a parity attachment circuit, in which the output signal is subjected to signal-processing such as attaching an error correction parity signal and outputting in serial order the resulting parity attached image and sound signals with a given transmission format, to a modulation circuit. The modulation circuit then modulates the serial signal in accordance with the characteristics of a transmission line, and the frequency band. For example, in the case of transmission via an electric radio wave, the signal is subjected to four-phase modulation (QPSK-modulation). A transmission circuit then outputs the resultant modulated signal to a transmission channel. Therefore, high-speed recording with a format identical to that of normal-speed recording, is allowed to be recorded onto the magnetic tape.
According to the aforementioned conventional technologies, for a MPEG-2 based transmission/reception of MPEG-2 based video data, uncompressed audio data, and user data, a problem exists where there is difficulty in identifying the uncompressed audio data and user data, since both the uncompressed audio data and the user data are PES private streams.
In addition, when an error correction code, an error detection code, and the other related connections unique to a recording apparatus, are attached to video data, they are combined into a PES private stream. A transport stream is then fabricated from the transmitted/received PES stream. In this case, a problem arises when the video data separated from a received data cannot be identified as MPEG-2 based video data, and when it is not able to be decoded.
Furthermore, since different transport streams are fabricated for the 525/59.94 component signal and the 625/50 component signal, respectively, corresponding different independent circuits are required.
Additionally, the ratios of video data, uncompressed audio data, user data to a frame of video data, and their locations to the frame are not fixed. Therefore, an identification circuit to identify the received data as video or uncompressed data is required.
Furthermore, since protection of a transport header is not made, it is impossible to decode compressed video data when the transport header has not been detected at least once, owing to a possible occurrence of a code error or other related errors during transmission. This problem may cause long time error propagation for the subsequent bits.
The aforementioned references 1 to 3 involve the following problems: First, according to the reference 1, no more than an image signal is processed. Thus, the reference 1 has a completely different technological idea from that of the present invention allowing to transmit/receive uncompressed audio data and user data as well as compressed video data. Secondly, according to the reference 2, not only image data but also sound data and time data is handled. However, this data is reproduced by the CD-I, and EFM-encoded. Therefore, The technological idea of reference 2 is quite different from the present invention handling MPEG based compressed video data. Lastly, according to the reference 3, the technology of compressing a digital image signal and a digital sound signal in their time axes, and bit-compressing them, is disclosed. However, no technology of MPEG-2-basis-compressing video data is disclosed. In addition, the compression approach of the reference 3 is quite different from that of the present invention.
Accordingly, the primary objective of the present invention is to provide a data transmission/reception method and apparatus, which will MPEG-2-basis-transmit and -receive digital video/audio/user data to and from a recording medium, such as an optical disk decoder, achieved with high efficiency and a low rate of error.
Further objectives of the present invention are as follows:
To provide a data transmission/reception apparatus for identifying audio data and user data.
To provide a data transmission/reception apparatus for successfully decoding video data even though an error correction code and an error detection code unique to a recording apparatus are attached to the video data.
To provide a data transmission/reception apparatus, which utilizes the same circuit for processing the 525/59.94 component signal and the 625/50 component signal.
To provide a data transmission/reception apparatus for identifying a received data as video data, audio data, or user data.
To provide a data transmission/reception apparatus for safely receiving a transport header even though the transport header cannot be detected owing to a possible occurrence of a code error during transmission.
According to an aspect of the present invention, a data transmission apparatus, which receives input data including at least MPEG-2 based video data and audio data, and transmitting the resultant transmission data, comprising: separation means for separating the input data into MPEG-2 based video data and audio data; first temporary memory circuit for storing the MPEG-2 based video data separated by the separation circuit, as the first data stored, and reading out the first data stored, as the first out-read data; second temporary memory circuit for storing the audio data separated from the separation means as the second data stored, and reading out the second data stored, as a second out-read data; combination circuit for combining the first out-read data and the second out-read data, and outputting the resultant combined data; PES private data attachment circuit for attaching a PES private data to the combined data, outputting the first attached data; PTS generation/attachment circuit for generation of a presentation time stamp PTS, attaching the presentation time stamp to the first attached data, outputting the resulting second attached data; PES header attachment circuit for attaching a PES header to the second attached data, outputting the resultant third attached data; transport header attachment circuit for attaching a transport header to the third attached data, outputting the resultant fourth attached data; a means for transmitting the fourth attached data, as transmission data.
As for the aforementioned data transmission apparatus, the received data may be made up of just MPEG-2 based video data and audio data. In this case, the third temporary memory circuit will not be necessary. In addition, the PTS generation/attachment circuit can also be omitted. Accordingly, the first attached data will be transmitted, as a second attached data, from the PES private data attachment circuit to the PES header attachment circuit.
According to an aspect of the present invention, a data reception apparatus, which receives transmission data, as received data, transmitted from the aforementioned data transmission apparatus, and outputting the resultant output data, comprising: transport header separation circuit for separating a transport header from the received data, outputting the resultant first separated data; PES header separation circuit for separating a PES header from the first separated data, outputting the resultant second separated data; PTS detection circuit for detecting a presentation time stamp PTS from the second separated data, outputting the resultant third separated data; PES private data separation circuit for separating a PES private data from the third separated data, outputting the resultant fourth separated data; separation means for separating a MPEG-2 based video data and audio data from the fourth separated data; first temporary memory circuit for storing the MPEG-2 based video data, as the first data stored, separated by the separation means, and reading out the first data stored, as the first out-read data; second temporary memory circuit for storing the audio data separated, as the second data stored, by the separation circuit, and reading out the second memory data, as a second out-read data; combination circuit for combining the first out-read data and the second out-read data together, and outputting the resultant combined data; means for outputting the combined data as output data.
As for the aforementioned data reception apparatus, when the data received by the data transmission apparatus is made up of only MPEG-2 based video data and audio data, the third temporary memory circuit can be omitted. In addition, the PTS detection circuit can also be omitted. Accordingly, the second attached data will be transmitted as the third attached data, from the PES header separation circuit to the PES private data separation circuit.
As an example, the aforementioned user data includes system data, an error correction code, and an error detection code, as in the following example:
Furthermore, letting LA, LB, LC, LD, and LE be: the length of the first PES stream made up of MPEG-2 based video data; the length of a second PES stream made up of the MPEG-2 based audio data; the length of a third PES stream made up of the aforementioned system data; the length of a fourth PES stream made up of the aforementioned error correction code; and the length of a fifth PES stream made up of the aforementioned error detection code, each of the LA, LB, LC, LD, and LE are preferably fixed for the 525/59.94 component signal and the 625/50 component signal.
Placing the first PES stream made up of MPEG-2 based video data; a second PES stream made up of the MPEG-2 based audio data; a third PES stream made up of the aforementioned system data; a fourth PES stream made up of the aforementioned error correction code; and a fifth PES stream made up of the aforementioned error detection code, on addresses PA, PB, PC, PD, and PE from the start of a frame respectively, the addresses PA, PB, PC, PD, and PE are preferably fixed for the 525/59.94 component signal and the 625/50 component signal.
Furthermore, the aforementioned error correction code and error detection code are attached for a data recording. They are preferably transmitted via a PES private stream.
Additionally, the locations of the aforementioned, MPEG-2 based video data, audio data, system data, error correction code, and error detection code are all preferably fixed to the frame synchronization. This can be attained by locking a transmission clock to a frame of the MPEG-2 based video data, and fixing the locations of the start and end of a frame, and the location of the end of a MPEG-2 based transport stream corresponding to a single frame for the 525/59.94 component signal and the 625/50 component signal.
The stream numbers for the MPEG-2 based video data, the audio data, the system data, the error correction code, and the error detection code are all preferably fixed. This can be attained by/with the transmission clock unlocking to a frame of the MPEG-2 based video data, starting a data transmission corresponding to a next frame at the beginning of a MPEG-2 transport stream of the 525/59.94 component signal and the 625/50 component signal just after the next frame starts.
A flag indicating each of the MPEG-2 based video data, the audio data, the system data, the error correction code, and the error detection code is preferably attached to the PES private data.
Furthermore, the transport header separation circuit preferably includes a transport header protection circuit to protect the transport header.
With the aforementioned configurations according to the present invention, the following results will be obtained:
For MPEG-2 based transmission/reception of video data, audio data (uncompressed audio data and compressed audio data not dependent upon the MPEG-2 standard), and user data, the audio data and the user data will be identified by transmitting a corresponding discriminant flag in the PES private data.
Video data dependent upon the MPEG-2 standard, in which an error correction code, an error detection code, and other related connections unique to a recording apparatus are attached to, will be directly decoded by a MPEG-2 decoder in the following method: First, separation is performed. Secondly, MPEG-2 based video data is put in a PES stream, while the error correction code, the error detection code, and the other related connections are put in a PES private stream. Thirdly, the PES and PES private streams are transmitted or received via another packet in the transport stream. Lastly, the resultant received data is subjected to error correction and error detection. This enables the MPEG-2 decoder to directly decode the MPEG-2 based video data.
The 525/59.94 component signal and the 625/50 component signal will be both processed through the same circuit. This can be realized by setting the frame frequency of the 625/50 component signal to be (5.005/6) times that of the 525/59.94 component signal, and the processing bit number per a frame of the former to be (6/5.005) times that of the latter, changing over between the two frame frequencies and processing bit numbers per a frame.
Received data will be identified as MPEG-2 based video data, audio data, or user data. This is achieved by fixing the occurred ratios of video data, audio data, and user data each to a frame of video data, and the location to the frame, for the 525/59.94 component signal and the 625/50 component signal.
The probability of an error occurring in the received data and its propagation will be drastically reduced by protecting the transport header. Protection enables for successful acquisition of the transport header, even though the possible-occurrence code transmission error prevents detection of the transport header.